Ren Junli

Preparation of xylan citrate--a potential adsorbent for industrial wastewater treatment.

The novel and degradable xylan citrate was prepared by the environmental-friendly semi-dry oven method. Xylan reacted with citric acid (CA) to yield xylan citrate at high temperature. The influence of the different weight ratios of CA and xylan on the product yield, the carboxyl group content and degree of esterification were comparatively discussed. The results showed that there were higher carboxyl group content and degree of esterification in modified xylan than native xylan. The product yield of 128.2%, the carboxyl group content of 1174.3 meq/100 g and degree of esterification of 33.1% were achieved at the CA/xylan weight ratio of 2.4 in the absence of catalyst. Furthermore, the adsorption capacity of xylan after modification was improved greatly. These materials with better properties can enhance their water affinity, and improve their adsorption of copper ions and methyl orange in aqueous solution due to carboxyl groups.

Preparation and characterization of sugarcane bagasse hemicellulosic derivatives containing quaternary ammonium groups in various media

Abstract To increase the solubility and produce cationic or ampholytic polymers as beater additives in papermaking from native hemicelluloses, quaternization of hemicelluloses were performed by reacting hemicelluloses with 3-chloro-2- hydroxypropyltrimethylammonium chloride (CHMAC) and preferably with 2,3- epoxypropyltrimethylammonium chloride (ETA) in aqueous sodium hydroxide, homogenously in dimethyl sulfoxide (DMSO), and completely heterogeneously in ethanol/water, respectively. The extent of modification was measured by degree of substitution (DS), and its value of up to 0.55 can be controlled by adjusting the molar ratio of reagent to hydroxyl functionality in hemicelluloses and the concentration of sodium hydroxide. The characterization of hemicellulosic derivatives was performed by elemental analysis, GPC, FT-IR and 13C NMR spectroscopy as well as thermal analysis. It was found that hemicellulosic polymer was significantly degraded in aqueous sodium hydroxide solution compared with in dimethyl sulfoxide and in ethanol/water systems under the conditions given. The thermal stability of modified hemicelluloses decreased after chemical modification, corresponding to the decreasing Mw of hemicelluloses derivatives.